diff --git a/clippy_lints/src/useless_conversion.rs b/clippy_lints/src/useless_conversion.rs index 95921518986b..7fa97b246991 100644 --- a/clippy_lints/src/useless_conversion.rs +++ b/clippy_lints/src/useless_conversion.rs @@ -1,14 +1,17 @@ use crate::utils::{ - match_def_path, match_trait_method, paths, same_tys, snippet, snippet_with_macro_callsite, span_lint_and_sugg, + is_type_diagnostic_item, match_def_path, match_trait_method, paths, same_tys, snippet, snippet_with_macro_callsite, + span_lint_and_help, span_lint_and_sugg, }; +use if_chain::if_chain; use rustc_errors::Applicability; use rustc_hir::{Expr, ExprKind, HirId, MatchSource}; use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty; use rustc_session::{declare_tool_lint, impl_lint_pass}; declare_clippy_lint! { - /// **What it does:** Checks for `Into`/`From`/`IntoIter` calls that useless converts - /// to the same type as caller. + /// **What it does:** Checks for `Into`, `TryInto`, `From`, `TryFrom`,`IntoIter` calls + /// that useless converts to the same type as caller. /// /// **Why is this bad?** Redundant code. /// @@ -26,7 +29,7 @@ declare_clippy_lint! { /// ``` pub USELESS_CONVERSION, complexity, - "calls to `Into`/`From`/`IntoIter` that performs useless conversions to the same type" + "calls to `Into`, `TryInto`, `From`, `TryFrom`, `IntoIter` that performs useless conversions to the same type" } #[derive(Default)] @@ -36,6 +39,7 @@ pub struct UselessConversion { impl_lint_pass!(UselessConversion => [USELESS_CONVERSION]); +#[allow(clippy::too_many_lines)] impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) { if e.span.from_expansion() { @@ -63,12 +67,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion { let b = cx.tables.expr_ty(&args[0]); if same_tys(cx, a, b) { let sugg = snippet_with_macro_callsite(cx, args[0].span, "").to_string(); - span_lint_and_sugg( cx, USELESS_CONVERSION, e.span, - "useless conversion", + "useless conversion to the same type", "consider removing `.into()`", sugg, Applicability::MachineApplicable, // snippet @@ -84,22 +87,70 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion { cx, USELESS_CONVERSION, e.span, - "useless conversion", + "useless conversion to the same type", "consider removing `.into_iter()`", sugg, Applicability::MachineApplicable, // snippet ); } } + if match_trait_method(cx, e, &paths::TRY_INTO_TRAIT) && &*name.ident.as_str() == "try_into" { + if_chain! { + let a = cx.tables.expr_ty(e); + let b = cx.tables.expr_ty(&args[0]); + if is_type_diagnostic_item(cx, a, sym!(result_type)); + if let ty::Adt(_, substs) = a.kind; + if let Some(a_type) = substs.types().next(); + if same_tys(cx, a_type, b); + + then { + span_lint_and_help( + cx, + USELESS_CONVERSION, + e.span, + "useless conversion to the same type", + None, + "consider removing `.try_into()`", + ); + } + } + } }, ExprKind::Call(ref path, ref args) => { - if let ExprKind::Path(ref qpath) = path.kind { - if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id() { - if match_def_path(cx, def_id, &paths::FROM_FROM) { - let a = cx.tables.expr_ty(e); - let b = cx.tables.expr_ty(&args[0]); - if same_tys(cx, a, b) { + if_chain! { + if args.len() == 1; + if let ExprKind::Path(ref qpath) = path.kind; + if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id(); + let a = cx.tables.expr_ty(e); + let b = cx.tables.expr_ty(&args[0]); + + then { + if_chain! { + if match_def_path(cx, def_id, &paths::TRY_FROM); + if is_type_diagnostic_item(cx, a, sym!(result_type)); + if let ty::Adt(_, substs) = a.kind; + if let Some(a_type) = substs.types().next(); + if same_tys(cx, a_type, b); + + then { + let hint = format!("consider removing `{}()`", snippet(cx, path.span, "TryFrom::try_from")); + span_lint_and_help( + cx, + USELESS_CONVERSION, + e.span, + "useless conversion to the same type", + None, + &hint, + ); + } + } + + if_chain! { + if match_def_path(cx, def_id, &paths::FROM_FROM); + if same_tys(cx, a, b); + + then { let sugg = snippet(cx, args[0].span.source_callsite(), "").into_owned(); let sugg_msg = format!("consider removing `{}()`", snippet(cx, path.span, "From::from")); @@ -107,7 +158,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UselessConversion { cx, USELESS_CONVERSION, e.span, - "useless conversion", + "useless conversion to the same type", &sugg_msg, sugg, Applicability::MachineApplicable, // snippet diff --git a/clippy_lints/src/utils/paths.rs b/clippy_lints/src/utils/paths.rs index b3ad2ad9d998..779da7e6bf23 100644 --- a/clippy_lints/src/utils/paths.rs +++ b/clippy_lints/src/utils/paths.rs @@ -128,8 +128,10 @@ pub const TO_OWNED_METHOD: [&str; 4] = ["alloc", "borrow", "ToOwned", "to_owned" pub const TO_STRING: [&str; 3] = ["alloc", "string", "ToString"]; pub const TO_STRING_METHOD: [&str; 4] = ["alloc", "string", "ToString", "to_string"]; pub const TRANSMUTE: [&str; 4] = ["core", "intrinsics", "", "transmute"]; +pub const TRY_FROM: [&str; 4] = ["core", "convert", "TryFrom", "try_from"]; pub const TRY_FROM_ERROR: [&str; 4] = ["std", "ops", "Try", "from_error"]; pub const TRY_INTO_RESULT: [&str; 4] = ["std", "ops", "Try", "into_result"]; +pub const TRY_INTO_TRAIT: [&str; 3] = ["core", "convert", "TryInto"]; pub const VEC: [&str; 3] = ["alloc", "vec", "Vec"]; pub const VEC_AS_MUT_SLICE: [&str; 4] = ["alloc", "vec", "Vec", "as_mut_slice"]; pub const VEC_AS_SLICE: [&str; 4] = ["alloc", "vec", "Vec", "as_slice"]; diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 8211a57b5643..f63301c7db0a 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -2421,7 +2421,7 @@ pub static ref ALL_LINTS: Vec = vec![ Lint { name: "useless_conversion", group: "complexity", - desc: "calls to `Into`/`From`/`IntoIter` that performs useless conversions to the same type", + desc: "calls to `Into`, `TryInto`, `From`, `TryFrom`, `IntoIter` that performs useless conversions to the same type", deprecation: None, module: "useless_conversion", }, diff --git a/tests/ui/useless_conversion.stderr b/tests/ui/useless_conversion.stderr index 7df3507edfd9..84ec53702788 100644 --- a/tests/ui/useless_conversion.stderr +++ b/tests/ui/useless_conversion.stderr @@ -1,4 +1,4 @@ -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:6:13 | LL | let _ = T::from(val); @@ -10,55 +10,55 @@ note: the lint level is defined here LL | #![deny(clippy::useless_conversion)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^ -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:7:5 | LL | val.into() | ^^^^^^^^^^ help: consider removing `.into()`: `val` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:19:22 | LL | let _: i32 = 0i32.into(); | ^^^^^^^^^^^ help: consider removing `.into()`: `0i32` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:51:21 | LL | let _: String = "foo".to_string().into(); | ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `"foo".to_string()` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:52:21 | LL | let _: String = From::from("foo".to_string()); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `From::from()`: `"foo".to_string()` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:53:13 | LL | let _ = String::from("foo".to_string()); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `"foo".to_string()` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:54:13 | LL | let _ = String::from(format!("A: {:04}", 123)); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `format!("A: {:04}", 123)` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:55:13 | LL | let _ = "".lines().into_iter(); | ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `"".lines()` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:56:13 | LL | let _ = vec![1, 2, 3].into_iter().into_iter(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![1, 2, 3].into_iter()` -error: useless conversion +error: useless conversion to the same type --> $DIR/useless_conversion.rs:57:21 | LL | let _: String = format!("Hello {}", "world").into(); diff --git a/tests/ui/useless_conversion_try.rs b/tests/ui/useless_conversion_try.rs new file mode 100644 index 000000000000..3787ea991445 --- /dev/null +++ b/tests/ui/useless_conversion_try.rs @@ -0,0 +1,42 @@ +#![deny(clippy::useless_conversion)] + +use std::convert::{TryFrom, TryInto}; + +fn test_generic(val: T) -> T { + let _ = T::try_from(val).unwrap(); + val.try_into().unwrap() +} + +fn test_generic2 + Into, U: From>(val: T) { + // ok + let _: i32 = val.try_into().unwrap(); + let _: U = val.try_into().unwrap(); + let _ = U::try_from(val).unwrap(); +} + +fn main() { + test_generic(10i32); + test_generic2::(10i32); + + let _: String = "foo".try_into().unwrap(); + let _: String = TryFrom::try_from("foo").unwrap(); + let _ = String::try_from("foo").unwrap(); + #[allow(clippy::useless_conversion)] + { + let _ = String::try_from("foo").unwrap(); + let _: String = "foo".try_into().unwrap(); + } + let _: String = "foo".to_string().try_into().unwrap(); + let _: String = TryFrom::try_from("foo".to_string()).unwrap(); + let _ = String::try_from("foo".to_string()).unwrap(); + let _ = String::try_from(format!("A: {:04}", 123)).unwrap(); + let _: String = format!("Hello {}", "world").try_into().unwrap(); + let _: String = "".to_owned().try_into().unwrap(); + let _: String = match String::from("_").try_into() { + Ok(a) => a, + Err(_) => "".into(), + }; + // FIXME this is a false negative + #[allow(clippy::cmp_owned)] + if String::from("a") == TryInto::::try_into(String::from("a")).unwrap() {} +} diff --git a/tests/ui/useless_conversion_try.stderr b/tests/ui/useless_conversion_try.stderr new file mode 100644 index 000000000000..b765727c168f --- /dev/null +++ b/tests/ui/useless_conversion_try.stderr @@ -0,0 +1,79 @@ +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:6:13 + | +LL | let _ = T::try_from(val).unwrap(); + | ^^^^^^^^^^^^^^^^ + | +note: the lint level is defined here + --> $DIR/useless_conversion_try.rs:1:9 + | +LL | #![deny(clippy::useless_conversion)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^ + = help: consider removing `T::try_from()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:7:5 + | +LL | val.try_into().unwrap() + | ^^^^^^^^^^^^^^ + | + = help: consider removing `.try_into()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:29:21 + | +LL | let _: String = "foo".to_string().try_into().unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `.try_into()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:30:21 + | +LL | let _: String = TryFrom::try_from("foo".to_string()).unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `TryFrom::try_from()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:31:13 + | +LL | let _ = String::try_from("foo".to_string()).unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `String::try_from()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:32:13 + | +LL | let _ = String::try_from(format!("A: {:04}", 123)).unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `String::try_from()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:33:21 + | +LL | let _: String = format!("Hello {}", "world").try_into().unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `.try_into()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:34:21 + | +LL | let _: String = "".to_owned().try_into().unwrap(); + | ^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `.try_into()` + +error: useless conversion to the same type + --> $DIR/useless_conversion_try.rs:35:27 + | +LL | let _: String = match String::from("_").try_into() { + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider removing `.try_into()` + +error: aborting due to 9 previous errors +